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April 22, 2010

Bye bye genetic determinism

How important are genes in determining how we are and become? Obviously, genes are quite important. Genes contain the instructions which lead to the formation of proteins, the molecules which play vital functions such as to help create cells. So, genes are definitely important. But how important are they? Or: how are they important?

The old view of genetic influence was an additive model in which genes (nature) and environment (nurture) each had a separate influence. The nature-nurture debates that got much attention tried to establish how great the relative influence of nature and nurture respectively were. This old view is visualized as follows (page 26):

The new interactionist (GxE) model describes how genes 'constantly respond to, and interact with, a wide range of internal and external stimuli - nutrition, hormones, sensory input, physical and intellectual activity, and other genes - to produce a unique, custom-tailored human machine for each person's unique circumstance.' The simple presence of a gene does not guarantee that specific types or numbers of proteins will be built. First, the gene has to be 'switched on' or expressed before this happens. According to Shenk, this interactionist view can be visualized as follows:

Briefly, this model shows how genes continuously interact with everything else that is happening in your life. This interaction shapes how we develop.